Object.prototype.toString

// '[object Null]'
Object.prototype.toString.call(null)
// '[object Undefined]'
Object.prototype.toString.call(undefined)
// '[object Number]'
Object.prototype.toString.call(0)
Object.prototype.toString.call(NaN)
Object.prototype.toString.call(new Number(123))
// '[object String]'
Object.prototype.toString.call("")
Object.prototype.toString.call(new String("123"))
// '[object Boolean]'
Object.prototype.toString.call(true)
Object.prototype.toString.call(false)
// '[object Object]'
Object.prototype.toString.call({})
// '[object RegExp]'
Object.prototype.toString.call(/\d/)
// '[object Date]'
Object.prototype.toString.call(new Date())
// '[object Function]'
Object.prototype.toString.call(function(){})
Object.prototype.toString.call(Date)
Object.prototype.toString.call(Function)
Object.prototype.toString.call(Boolean)
Object.prototype.toString.call(String)
Object.prototype.toString.call(Number)
// '[object Math]'
Object.prototype.toString.call(Math)